Don't be afraid to say you're sorry. I know you don't hear that phrase a lot around our house. I don't say it very often. And your dad says it even less. I haven't been the best role model in that area. But, I know that when someone apologizes to me for something, it means the world to me. I know a lot of times I'll look back at a situation and see a need to apologize for something, but sometimes I put it off or I don't know how to say it and it goes unsaid. Or sometimes it does come out, but so much time has passed, it just doesn't have the same affect. Just like a thank you note you receive a couple days after giving a gift or doing something nice means a little more than one that comes months later. Whoever said "Better late than never" was likely a huge procrastinator.
Of all five of you, there's one who sees mistakes and immediately apologizes. Yes, sometimes it's to soften things a little in anticipation of a consequence and to elicit some sympathy, but it's usually more than that. It sounds sincere and makes me feel that you really regret something you've done wrong. For the other four of you - you know who you are - it's like pulling teeth to get those words to come out of your mouth, even if you know unequivocally that you were in the wrong.
It is important. Practice it. Learn to be apologetic. Learn to admit your mistakes and try to make them right.